1. Field of the Invention
The present invention relates to an optical recording medium-manufacturing apparatus for manufacturing an optical recording medium by punching a central hole through a disk-shaped substrate having a resin layer formed on one side thereof.
2. Description of the Related Art
In general, when an optical recording medium (optical disk), such as a CD or a DVD, is manufactured, a thin film, such as a light-reflecting layer, is formed on a disk-shaped substrate having grooves and lands formed in a surface thereof by injection molding, and then a resin layer as a protective layer is formed on the thin film by the spin-coating method such that the protective layer covers the thin film. Further, when a writable optical recording medium, such as a CD-R, a CD-RW, a DVD-R, or a DVD-RW, is manufactured, thin films, such as a light-reflecting layer and a recording layer, are sequentially formed on a surface of a substrate, and then a resin layer as a protective layer is formed on top of the thin films by the spin-coating method such that the protective layer covers the thin films. If the optical recording medium thus manufactured has variation in the film thickness of the resin layer thereof, it is difficult to reliably prevent damage from occurring to the thin film. Therefore, in the formation of a resin layer, it is necessary to spin-coat the entire surface of a substrate with a resin material for forming a resin layer, to a uniform thickness. Further, to form a resin layer having a uniform thickness on a substrate by the spin-coating method, it is preferable to drop a resin material onto the center of a substrate being rotated. However, it is necessary to form a central hole in the center of an optical recording medium, for enabling clamping (chucking) e.g. by a recording and reproducing apparatus, which makes it difficult to drop a resin material onto the center of a substrate during execution of spin-coating operation. To overcome this problem, the present inventors have proposed in Japanese Patent Application No. 2002-196415 an optical recording medium-manufacturing apparatus (hereinafter also referred to as the “manufacturing apparatus”) which is configured to drop a resin material onto a substrate before forming a central hole, thereby forming a resin layer with a uniform thickness, and then punch the central hole such that the central hole extends through the substrate and the resin layer.
In the proposed manufacturing apparatus, first, an information-recording surface of a disk-shaped substrate (substrate) having no central hole formed in a central portion thereof is spin-coated with a resin for forming a light transmission layer. In this case, differently from the CD and the DVD of the type referred to hereinabove, an optical recording medium manufactured by the manufacturing apparatus proposed by the present inventors is configured such that in recording or reproducing record data, a laser beam is caused to enter the medium from a front surface side of a resin layer formed on a thin film. Therefore, in the manufacturing apparatus, when the optical recording medium is manufactured, a light transmission layer for transmitting a laser beam therethrough is formed in place of the protective layer in the above example. More specifically, an ultraviolet-curing resin, for example, is dropped onto the center (portion to be formed with a central hole afterwards) of a substrate being rotated by a coating device such that the resin material is caused to expand toward the periphery of the substrate by centrifugal force generated by rotation of the substrate. In doing this, the rotational speed of the substrate is properly adjusted, whereby the resin material is uniformly coated on the entire information-recording surface. Then, an ultraviolet ray is irradiated onto the resin coated on the substrate such that the resin is cured to form a light transmission layer.
Then, a circular cut having a diameter approximately equal to that of the central hole is formed in the light transmission layer in an area of the light transmission layer where a central hole is to be formed. More specifically, the substrate is rotated in a state where a blade of a tool is pushed into the light transmission layer, whereby a cut having a depth approximately equal to the thickness of the light transmission layer is formed in the light transmission layer. Subsequently, the substrate is transferred by a transfer mechanism from a processing location for forming a cut (hereinafter also referred to as the “cut-forming location”) to a location for forming a central hole (hereinafter also referred to as the “central hole-forming location”). Then, a hollow cylindrical punching tool is pushed into the substrate from the side where the light transmission layer has been formed, to thereby punch a central hole through the substrate. In doing this, since the cut has been formed in the light transmission layer prior to punching the central hole, peeling-off or formation of burrs is prevented from occurring to the light transmission layer during formation of the central hole. By carrying out the steps described above, the optical recording medium is completed. Thereafter, the optical recording medium is transferred by the transfer mechanism from the central hole-forming location to a stack location for stacking completed optical recording media.
However, from the study of the proposed manufacturing apparatus, the present inventors found out the following points for improvement: In the proposed manufacturing apparatus, a substrate having a cut formed therein is transferred from the cut-forming location to the central hole-forming location by the transfer mechanism. In this case, the transfer mechanism employed for this type of manufacturing apparatus includes pivot arms each having a sucking portion mounted at a foremost end thereof for sucking a substrate (optical recording medium) thereto, and is capable of transferring the substrate held thereat by suction along an arcuate path of the sucking portion at the foremost end of the pivot arm rotated about the root (proximal) end thereof. Further, a cut-forming machine for forming a cut and a punching machine for punching the disk-shaped substrate are provided with vertical movement mechanisms for vertically moving a tool for forming a cut and a punching tool, respectively. This requires the transfer mechanism to be arranged such that the transfer mechanism does not interfere with the vertical motions of these tools, which makes it difficult to arrange the transfer mechanism very close to the cut-forming machine and the punching machine. Accordingly, it is necessary to install the transfer mechanism at a location away from the cut-forming machine and the punching machine, and transfer substrates by its long pivot arms. As a consequence, it is necessary to secure a large pivotal motion space which allows the pivot arms and substrates held thereat to move. This makes it preferable to make the area occupied by the whole manufacturing apparatus as small as possible. Further, in the case of the transfer mechanism employing the pivot arms, it is difficult to accurately control the pivoting angle of each pivot arm, and the start and stop of suction of a substrate by the sucking portion of the pivot arm, and hence there is also a problem of difficulty to perform accurate transfer of a substrate from the cut-forming location (where the cut-forming machine is installed) to the central hole-forming location (where the central hole-forming machine is installed).
Further, in the manufacturing apparatuses proposed by the inventors, when the punching of a central hole by the punching machine is completed, very small cuttings sometimes remain adhering to the central hole or its vicinity, and hence it is necessary to remove the cuttings. Further, in the case of the manufacturing apparatus proposed by the present inventors, when a tool pushed into the light transmission layer on a substrate in forming a cut, or a punching tool pushed into the substrate in punching a central hole, is moved away from the substrate, the substrate with the tool or the punching tool stuck therein is sometimes moved together with the tool. In such a case, the efficiency in manufacturing optical recording media is degraded since an operator has to remove the substrate from the tool by manual operation, and hence improvement in this point is desired.